Manifold heat cross over physics and benifits

Krazy,
We are still going around and around but that is fine with me. I reckon you are disagreeing w me because my posts must not be clear or you have not read them all. I have literally been stating exactly what you stated below, for this entire thread. :) I agree.

The only thing I may beg to differ on is the density of intake charge based on two engines: One a 1975 V8 w all factory systems functioning perfectly and the other a 2001 4.7 Dodge with all systems good (or any modern v8).
Both engines running in a test cell with identical air inlet temp.


If you compare the process of a heated carbureted wet intake manifold to a non heated plastic MPFI manifold you will get similar results (similar objectives achieved totally differently) regarding fuel atomization but the plastic mpfi will yield a slightly cooler charge, due to the lack of heat crossover, oil splash and conduction but still yeild efficient (obviously more efficient) fuel distribution. In addition you get better flow, runner and plenum tuning more economically due to manufacturing advantages.

krazykuda said

Not really. MPFI manifolds don't have to carry the fuel from the throttle plates into the cylinder. You don't have to keep it suspended in the air mixture through the port. You just spray the fuel past the valve into the cylinder. Since the fuel is not being carried through the ports, it doesn't have the opportunity to condense in the ports because you are only moving dry air.

With a cold engine and cold port passages, sometimes the fuel will condense on the port walls because they cool the mixture to where the fuel condenses on the port walls for a carbureted engine. Since the FI engine is not carrying any fuel, it is not there to condense on the port walls.

At the same temperature, the density of the intake air is the same for both carbureted and fuel injected engines.

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